60 psychology undergraduate students from New York University. Participants randomly divided into 3 groups.

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Procedure for all

Participant seated in sound shielded room+wired up to galvanic skin response (GSR) and heart rate monitors. Machine calibrated for 5 mins then baseline measurement taken. GSR analyses taken at onset of tone, second half of tone+in response to photos.

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Group 1 procedure

Given actual control over length of time to view photos. Could press a button to terminate photo for max of 35 seconds. Told tone would precede each photo.

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Group 2 procedure

Saw photos for same time as group 1, warned photos were 60 seconds apart+told how long photo would be viewed for. Told 10 second warning tone precedes each photo. No control but knew what would happen.

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Group 3 procedure

Told from time to time they would see photos and hear tones. Had no control or predictability.

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Findings

Data from heart rate monitors deemed as invalid and so discarded. Group 2 most stressed by tone as they knew what would happen, but had no control. Group 1 less stressed by photos than group 2+3, because they had control.

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Conclusion

Results suggest that having control to terminate aversive stimuli reduces the stressful impact of those stimuli.